Aqueous graphene-containing coating composition and method of making the same

Abstract

The present application provides a graphene-containing water-based paint composition and a preparation method thereof, wherein the dispersibility and uniformity of graphene in an epoxy resin paint are significantly improved by surface modification of the graphene, and the physical and chemical properties of the epoxy resin coating are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of graphene coating modification, and more particularly to a method for improving the chemical properties of epoxy resin coatings using modified graphene. Background Technology

[0002] Epoxy resin is a high-performance thermosetting plastic widely used in various industries due to its unique chemical structure and properties. Epoxy resin is a high-molecular polymer containing more than two epoxy groups, and its molecular structure is defined as (C...). 11 H 12 O3)n. This substance is typically formed by the condensation of epichlorohydrin with bisphenol A or polyols, belonging to a large class of specific polymers. Among them, bisphenol F type epoxy resin is one of the most common epoxy resins, which is prepared by reacting bisphenol F (a specific type of phenolic compound) with epoxy compounds. Compared with bisphenol A type epoxy resin, bisphenol F type epoxy resin offers different performance characteristics in certain applications, with better chemical and thermal stability.

[0003] Epoxy resins have the following characteristics:

[0004] (1) Excellent bonding properties: Epoxy resin can form strong bonds with many different types of materials (including metals, glass, wood, etc.), making it an ideal choice for manufacturing composite materials and adhesives; (2) High mechanical strength: Cured epoxy resin has high tensile strength, compressive strength and flexural strength, making it particularly valuable in structural applications; (3) Excellent chemical resistance: Epoxy resin exhibits good resistance to many chemicals (including acids, alkalis, solvents, etc.), making it applicable in chemical processing and storage fields; (4) Good electrical insulation properties: Epoxy resin has high electrical insulation and low dielectric constant, suitable for... Used in the electronics and electrical fields, such as insulators, circuit boards, etc.; (5) Heat resistance: Epoxy resin can withstand high working temperatures, and epoxy resin with specific formulations can even maintain its performance under continuous high temperature conditions; (6) Low shrinkage: During the curing process, the volume shrinkage of epoxy resin is very small, which helps to maintain the dimensional stability and overall strength of the finished product; (7) Customizability: By changing the type and ratio of curing agent or adding other modifiers, the final performance of epoxy resin can be adjusted to meet the needs of specific applications; (8) Weather resistance: Epoxy resin has good UV resistance and oxidation resistance, and can be used in outdoor environments for a long time without aging.

[0005] These properties make epoxy resins play an important role in many fields such as aerospace, automotive manufacturing, electronics and electrical engineering, energy equipment, construction, and civil engineering. However, the application of epoxy resins also faces some limitations, such as toxicity before curing and sensitivity to certain chemicals. Therefore, special attention must be paid to safety during handling and use.

[0006] Graphene, a simple two-dimensional structure, is composed of carbon atoms. Early research on this material began with the development of X-ray crystallography. Researchers attempted to prepare graphene using chemical exfoliation and vapor deposition methods, but these methods proved unsuccessful, leading many researchers to abandon this area of ​​research. However, in 2004, Novoselov et al. successfully prepared monolayer graphene for the first time using mechanical exfoliation. This achievement brought widespread attention to graphene's unique two-dimensional structure, sparking a research boom and leading to its widespread applications. Although graphene is isolated from graphite, various carbon-based materials with different dimensions can be created by altering the structure of monolayer graphene. For example, twisting monolayer graphene can generate zero-dimensional fullerenes, one-dimensional carbon nanotubes, or three-dimensional graphite stacks. It is this special atomic structure of monolayer graphene that endows it with outstanding mechanical, thermal, and electrical properties.

[0007] The combination of epoxy resin and graphene can significantly improve the properties of materials. Epoxy resin is a thermally resistant...

[0008] Graphene is a solid polymer widely used in adhesives, coatings, and composite materials.

[0009] Two-dimensional materials composed of honeycomb structures are known for their excellent mechanical properties, electrical conductivity, and thermal conductivity.

[0010] Advantages of combining epoxy resin and graphene:

[0011] (1) Enhanced mechanical properties: The addition of graphene can significantly improve the strength and stiffness of epoxy resin-based composite materials. This is because graphene has an extremely high specific surface area and excellent mechanical properties, which can effectively bear loads and transmit forces through composite materials.

[0012] (2) Improve electrical and thermal conductivity: The addition of graphene can significantly improve the electrical and thermal conductivity of epoxy resin, which is very important for applications that require electromagnetic shielding and thermal management.

[0013] (3) Increase heat resistance: Graphene can improve the thermal stability of epoxy resin, thereby enabling the composite material to work stably at higher temperatures.

[0014] (4) Improved chemical stability: The addition of graphene can improve the corrosion resistance and chemical stability of epoxy resin composites, extending the service life of the materials. Due to these improved properties, epoxy resin / graphene composites have potential applications in many fields, including:

[0015] (1) Aerospace: Used to manufacture lightweight yet high-strength structural components.

[0016] (2) Automobile: Used to improve the performance and durability of automobile parts.

[0017] (3) Electronic products: Used in circuit boards and electromagnetic shielding materials to improve heat dissipation performance.

[0018] (4) Energy storage: As an electrode material for supercapacitors and batteries, it improves the performance of energy storage devices.

[0019] Existing technologies include various examples of preparing high-performance coatings by mixing modified graphene with epoxy resin. For instance, Tianjin University disclosed a graphene-containing marine anti-corrosion and antifouling coating and its preparation method. Graphene, with its antibacterial properties, is added to epoxy resin as a filler through surface modification, thereby preparing a nanocomposite antifouling coating with antibacterial and corrosion-resistant properties. This invention adds graphene to epoxy resin as a marine antifouling coating, fully combining the excellent properties of both materials. This allows the coating to possess both antifouling and anti-corrosion properties. By combining graphene and epoxy resin, the antibacterial properties of graphene and the anti-corrosion properties of epoxy resin are organically combined, thus developing a novel antifouling coating with both corrosion resistance and antifouling properties. Graphene modification includes: (1) hydroxylation of graphene surface; (2) Graphene coupling: according to the mass ratio of surface-hydroxylated graphene to N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane 1:(3~6), surface-hydroxylated graphene and N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) are dissolved in deionized water, ultrasonically dispersed, heated and stirred, centrifuged, washed and dried, and ground to obtain coupled modified graphene. Specifically, the following steps are performed: the modified graphene and KH602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane) are dissolved in a small amount of deionized water at a mass ratio of mgraphene:mKH-602=1:(3~6); after stirring evenly, ultrasonically dispersed for 30 minutes. The system was heated and stirred at 60°C with a magnetic stirrer for 8–10 hours. The modified graphene was separated by centrifugation, washed three times with distilled water and twice with ethanol, and then dried in an oven at 60°C and ground.

[0020] Furthermore, CN105385330B, a method for chemically modifying polyurethane conductive coatings with carbon nanotubes, deserves special attention. This method involves grafting functionalized carbon nanotubes with polyacrylamide chloride, followed by grafting the reaction solution with a hydroxyl-containing polyurethane resin. Specifically, the remaining acrylamide groups react with the hydroxyl-containing polyurethane to obtain a carbon nanotube-modified polyurethane resin. Finally, the modified polyurethane is mixed with unmodified polyurethane to form the coating. This method utilizes active acrylamide groups to graft carbon nanotubes, followed by grafting with polyurethane, ensuring uniform dispersion and strong filling of carbon nanotubes in the coating. It also significantly improves the grafting rate of carbon nanotubes, effectively eliminating the aggregation of carbon nanotubes in organic matter, improving their dispersibility and conductivity in the polyurethane coating, and ultimately obtaining a highly dispersible nanocomposite polyurethane coating. This allows for the preparation of modified coatings with excellent antistatic and electromagnetic shielding properties. The beneficial effects are described as follows: The provided method for chemically modifying polyurethane conductive coatings with carbon nanotubes involves grafting functionalized carbon nanotubes with polyacrylamide chloride. The reaction solution is then grafted with a hydroxyl-containing polyurethane resin, utilizing the remaining acrylamide groups to react with the hydroxyl-containing polyurethane to obtain a carbon nanotube-modified polyurethane resin. Finally, the obtained modified polyurethane is mixed with unmodified polyurethane to prepare the coating. This method utilizes active acrylamide groups to graft carbon nanotubes, followed by grafting with polyurethane, ensuring the uniform dispersion and strong filling of carbon nanotubes in the coating. Furthermore, it significantly improves the grafting rate of carbon nanotubes, effectively eliminating the aggregation of carbon nanotubes in organic matter, improving their dispersibility in the polyurethane coating, and enhancing the conductivity of the coating. This results in a highly dispersible nanocomposite polyurethane coating, which can be used to prepare modified coatings with excellent antistatic and electromagnetic shielding properties. The most serious technical problem with this patent is that it uses the remaining acyl chloride groups to react with polyurethane containing hydroxyl groups to prepare polyurethane resin modified with carbon nanotubes. However, it is known in the art that the remaining acyl chloride groups are completely encapsulated in organic groups and are difficult to contact with the subsequent hydroxyl groups. In other words, it is difficult to achieve a complete and sufficient reaction between the remaining acyl chloride groups and the polyurethane containing hydroxyl groups through natural reactions alone, resulting in poor modification effect. Summary of the Invention

[0021] Based on the above, graphene is first pretreated with mixed acid to obtain fluffy graphene with good dispersibility. The surface of the fluffy graphene contains some functional groups to improve the dispersibility of the graphene. Then, the surface functional groups react with some of the acyl chlorides in the synthesized polymer to complete polymer grafting. The remaining acyl chlorides are fully exposed under hydrothermal conditions and react fully with the hydroxyl groups in the epoxy resin, ultimately realizing the full functionalization of the epoxy resin into graphene. Due to the encapsulation of the epoxy resin, the fully functionalized graphene is highly dispersed in the epoxy resin solution used in the subsequent coating preparation process. Under the curing reaction of the curing agent, a highly dispersed graphene epoxy resin coating structure is obtained, thereby significantly improving the physicochemical properties of the epoxy resin coating.

[0022] A graphene-containing aqueous coating composition comprises the following parts by weight:

[0023] 40-70 parts epoxy resin;

[0024] 15-20 parts of modified graphene powder;

[0025] 2-3 parts TBEP plasticizer;

[0026] 0.5-0.7 parts of TEGO270 wetting agent;

[0027] 0.2-0.3 parts of BD-3033 leveling agent;

[0028] Acrysol R8 thickener 0.1-0.3 parts;

[0029] 0.1-0.5 parts ammonia solution;

[0030] BYK163 dispersant 4-6 parts;

[0031] Dow Corning AFE-1410 defoamer, 0.2-0.5 parts;

[0032] 30-40 parts of curing agent;

[0033] 5-15 parts deionized water.

[0034] The modified graphene powder was prepared by the following steps: (a) Pretreatment: Commercially available graphene powder was placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid were added to form a mixed acid solution. The solution was heated to 90-98°C, cooled and refluxed with water for 4-5 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid was placed in a refrigerator and frozen for 5-6 hours. Then it was placed in a low-temperature vacuum freeze dryer and dried for 6-10 hours. The fluffy graphene powder was then taken out.

[0035] (b) Preparation of grafted polymer: Dissolve 68-90 mg of initiator AIBN and 4-5 ml of acryloyl chloride in 10-12 ml of 1,4-dioxane solvent, and then place them in a 60-70 ml reaction vessel. After the reaction vessel is dried and purged with nitrogen, it is stirred at 60-62 °C for 20-30 h.

[0036] (c) Modified graphene powder: Add 150-170 mg of graphene powder prepared in step (a) and 100-120 ml of 1,4-dioxane solvent to a nitrogen-filled reaction metal bottle with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). React at 60-70℃ for 36-40 h, then continuously introduce nitrogen gas. After natural cooling, add 220-240 ml of epoxy resin, seal the reaction vessel, and use nitrogen gas to control the gas pressure of the reaction gas in the metal bottle to 6-7 MPa. Turn off the nitrogen gas supply and heat the reaction vessel by programmed temperature increase. The programmed temperature increase is to heat to 95-100℃ at a rate of 1-2℃. Perform a solvothermal reaction for 24-48 h, stir the reaction for 48 h, and then allow it to cool naturally before removing it.

[0037] (d) Post-processing: Centrifuge at 8000-9000 rpm to obtain solid liquid, then wash with acetone and deionized water multiple times, freeze the solid wash in a refrigerator for 5-6 hours, and then dry in a low-temperature vacuum freeze dryer for 6-10 hours to remove the modified graphene powder.

[0038] The curing agent is a polyamine-based curing agent.

[0039] It is selected from ethylenediamine or diaminodiphenyl sulfone.

[0040] A method for preparing a graphene-containing aqueous coating composition includes the following steps:

[0041] (1) Preparation of modified graphene powder;

[0042] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder are placed in a reaction vessel according to the ratio and homogenized at 1200-1400 rpm for 5-10 min to obtain a dispersion.

[0043] (3) Add epoxy resin, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1200-1400 rpm for 5-10 min, add the remaining deionized water and stir evenly.

[0044] (4) Continue to add curing agent to step (3) and stir thoroughly for 30-40 minutes, then cure at 30-40℃ for 60-90 minutes.

[0045] Modified graphene powder is produced through the following steps:

[0046] (a) Pretreatment: Place commercially available graphene powder in a reaction vessel, then add concentrated nitric acid and concentrated sulfuric acid to form a mixed acid solution, heat to 90-98℃, cool with water and reflux for 4-5 hours, then cool to room temperature, filter and wash multiple times, place the brown graphene solid separation in a refrigerator to freeze for 5-6 hours, then put it into a low-temperature vacuum freeze dryer to dry for 6-10 hours, and take out the fluffy graphene powder.

[0047] (b) Preparation of grafted polymer: Dissolve 68-90 mg of initiator AIBN and 4-5 ml of acryloyl chloride in 10-12 ml of 1,4-dioxane solvent, and then place them in a 60-70 ml reaction vessel. After the reaction vessel is dried and purged with nitrogen, it is stirred at 60-62 °C for 20-30 h.

[0048] (c) Modified graphene powder: Add 150-170 mg of graphene powder prepared in step (a) and 100-120 ml of 1,4-dioxane solvent to a nitrogen-filled reaction metal bottle with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). React at 60-70℃ for 36-40 h, then continuously introduce nitrogen gas. After natural cooling, add 220-240 ml of epoxy resin organic dispersion, seal the reaction vessel, and use nitrogen gas to control the gas pressure of the reaction gas in the metal bottle to 6-7 MPa. Turn off the nitrogen gas supply and heat the reaction vessel by programmed temperature increase. The programmed temperature increase is to heat to 95-100℃ at a rate of 1-2℃. Perform a solvothermal reaction for 24-48 h, stir the reaction for 48 h, and then allow it to cool naturally before removing it.

[0049] (d) Post-processing: Centrifuge at 8000-9000 rpm to obtain solid liquid, then wash with acetone and deionized water multiple times, freeze the solid wash in a refrigerator for 5-6 hours, and then dry in a low-temperature vacuum freeze dryer for 6-10 hours to remove the modified graphene powder.

[0050] The epoxy resin dispersion is an epoxy resin and a 1,4-dioxane solvent in a mass ratio of 1:1.5-2.

[0051] Beneficial technical effects: The epoxy groups modified on the surface of graphene in this invention can further participate in the curing reaction of the epoxy resin matrix, forming a strong interfacial effect of chemical bond connection, so that graphene can effectively bear external load and improve physical and chemical mechanical properties; (2) Unreacted or buried acyl chloride groups are fully exposed under hydrothermal conditions and fully react with hydroxyl groups in epoxy resin, ultimately realizing the full functionalization of epoxy resin into graphene; The fully functionalized graphene, due to the encapsulation of epoxy resin, will be greatly dispersed in the epoxy resin solution used in the subsequent coating preparation process. Under the curing reaction of curing agent, a highly dispersed graphene epoxy resin coating structure is obtained, thereby significantly improving the physical and chemical properties of epoxy resin coating. Detailed Implementation Example 1

[0052] A method for preparing a graphene-containing aqueous coating composition includes the following steps:

[0053] (1) Preparation of modified graphene powder.

[0054] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder were placed in a reaction vessel according to the ratio and homogenized at 1200 rpm for 5 min to obtain a dispersion.

[0055] (3) Add epoxy resin emulsion, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1200 rpm for 5 min, add the remaining deionized water and stir evenly.

[0056] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir thoroughly for 30 min, then cure at 30°C for 60 min.

[0057] The weight proportions of each component in the coating are as follows: 40 parts epoxy resin emulsion; 15 parts modified graphene powder; 2 parts TBEP plasticizer; 0.5 parts TEGO270 wetting agent; 0.2 parts BD-3033 leveling agent; 0.1 parts Acrysol R8 thickener; 0.1 parts ammonia; 4 parts BYK163 dispersant; 0.2 parts Dow Corning AFE-1410 defoamer; 30 parts curing agent; and 5 parts deionized water.

[0058] Modified graphene powder is processed through the following steps: (a) Pretreatment: Commercially available graphene powder is placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid are added to form a mixed acid solution. The solution is heated to 90°C, cooled and refluxed for 4 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid is separated and frozen in a refrigerator for 5 hours. Then it is dried in a low-temperature vacuum freeze dryer for 6 hours, and the fluffy graphene powder is taken out.

[0059] (b) Preparation of grafted polymer: 68 mg of initiator AIBN and 4 ml of acryloyl chloride were dissolved in 10 ml of 1,4-dioxane solvent and then placed in a 60 ml reaction vessel. The reaction vessel was dried, purged with nitrogen, and stirred at 60 °C for 20-30 h.

[0060] (c) Modified graphene powder: Add 150 mg of graphene powder prepared in step (a) and 100 ml of 1,4-dioxane solvent to a nitrogen-filled reaction metal bottle with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). After reacting at 60°C for 36 h, continuously introduce nitrogen gas. After natural cooling, add 220 ml of epoxy resin organic dispersion, seal the reaction vessel, and use nitrogen gas to control the gas pressure of the reaction gas in the metal bottle to 6 MPa. Turn off the nitrogen gas supply and heat the reaction vessel by programmed temperature increase. The programmed temperature increase is to heat to 95°C at a rate of 1°C. Solvothermal reaction for 24 h, stirring reaction for 48 h, natural cooling, and removal.

[0061] (d) Post-processing: The solid liquid was obtained by centrifugation at 8000 rpm, and then washed multiple times with acetone and deionized water. The solid wash was placed in a refrigerator and frozen for 5 hours, and then placed in a low-temperature vacuum freeze dryer for 6 hours to remove the modified graphene powder.

[0062] The epoxy resin organic dispersion is an epoxy resin and a 1,4-dioxane solvent in a mass ratio of 1:1.5. Example 2

[0063] A method for preparing a graphene-containing aqueous coating composition includes the following steps:

[0064] (1) Preparation of modified graphene powder.

[0065] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder were placed in a reaction vessel according to the ratio and homogenized at 1300 rpm for 7.5 min to obtain a dispersion.

[0066] (3) Add epoxy resin emulsion, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1300 rpm for 7.5 min, add the remaining deionized water and stir evenly.

[0067] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir and mix thoroughly for 35 min, then cure at 35°C for 75 min.

[0068] The weight proportions of each component in the coating are as follows: 55 parts epoxy resin emulsion; 17.5 parts modified graphene powder; 2.5 parts TBEP plasticizer; 0.6 parts TEGO270 wetting agent; 0.25 parts BD-3033 leveling agent; 0.2 parts Acrysol R8 thickener; 0.3 parts ammonia; 5 parts BYK163 dispersant; 0.35 parts Dow Corning AFE-1410 defoamer; 35 parts curing agent; and 10 parts deionized water.

[0069] Modified graphene powder is processed through the following steps: (a) Pretreatment: Commercially available graphene powder is placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid are added to form a mixed acid solution. The solution is heated to 95°C, cooled and refluxed with cooling water for 4.5 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid separation is placed in a refrigerator and frozen for 5.5 hours. Then it is placed in a low-temperature vacuum freeze dryer and dried for 8 hours. The fluffy graphene powder is then removed.

[0070] (b) Preparation of grafted polymer: 79 mg of initiator AIBN and 4.5 ml of acryloyl chloride were dissolved in 11 ml of 1,4-dioxane solvent and then placed in a 65 ml reaction vessel. The reaction vessel was dried, purged with nitrogen, and stirred at 61 °C for 25 h.

[0071] (c) Modified graphene powder: Add 160 mg of graphene powder prepared in step (a) and 110 ml of 1,4-dioxane solvent to a nitrogen-filled reaction metal bottle with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). After reacting at 65°C for 38 h, continuously introduce nitrogen gas. After natural cooling, add 230 ml of epoxy resin organic dispersion, seal the reaction vessel, and use nitrogen gas to control the gas pressure of the reaction gas in the metal bottle to 6.5 MPa. Turn off the nitrogen gas supply and heat the reaction vessel by programmed temperature increase. The programmed temperature increase is to heat to 97.5°C at a rate of 1.5°C. Solvothermal reaction for 36 h, stirring reaction for 48 h, natural cooling, and removal.

[0072] (d) Post-processing: The solid liquid was obtained by centrifugation at 8500 rpm, and then washed multiple times with acetone and deionized water. The solid wash was placed in a refrigerator and frozen for 5.5 h, and then placed in a low-temperature vacuum freeze dryer for 8 h to dry. The modified graphene powder was then removed.

[0073] The epoxy resin organic dispersion is an epoxy resin and a 1,4-dioxane solvent in a mass ratio of 1:1.75. Example 3

[0074] A method for preparing a graphene-containing aqueous coating composition includes the following steps:

[0075] (1) Preparation of modified graphene powder.

[0076] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder were placed in a reaction vessel according to the ratio and homogenized at 1400 rpm for 10 min to obtain a dispersion.

[0077] (3) Add epoxy resin emulsion, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1400 rpm for 10 min, add remaining deionized water and stir evenly.

[0078] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir and mix thoroughly for 40 min, then cure at 40°C for 90 min.

[0079] The weight proportions of each component in the coating are as follows: 70 parts epoxy resin emulsion; 20 parts modified graphene powder; 3 parts TBEP plasticizer; 0.7 parts TEGO270 wetting agent; 0.3 parts BD-3033 leveling agent; 0.3 parts Acrysol R8 thickener; 0.5 parts ammonia; 6 parts BYK163 dispersant; 0.5 parts Dow Corning AFE-1410 defoamer; 40 parts curing agent; and 15 parts deionized water.

[0080] Modified graphene powder is processed through the following steps: (a) Pretreatment: Commercially available graphene powder is placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid are added to form a mixed acid solution. The solution is heated to 98°C, cooled and refluxed for 5 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid is separated and frozen in a refrigerator for 6 hours. Then it is dried in a low-temperature vacuum freeze dryer for 10 hours, and the fluffy graphene powder is taken out.

[0081] (b) Preparation of grafted polymer: 90 mg of initiator AIBN and 5 ml of acryloyl chloride were dissolved in 12 ml of 1,4-dioxane solvent and then placed in a 70 ml reaction vessel. The reaction vessel was dried, purged with nitrogen, and stirred at 62 °C for 30 h.

[0082] (c) Modified graphene powder: Add 170 mg of graphene powder prepared in step (a) and 120 ml of 1,4-dioxane solvent to a nitrogen-filled reaction metal bottle with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). After reacting at 70°C for 40 h, continuously introduce nitrogen gas. After natural cooling, add 240 ml of epoxy resin organic dispersion, seal the reaction vessel, and use nitrogen gas to control the gas pressure of the reaction gas in the metal bottle to 7 MPa. Turn off the nitrogen gas supply and heat the reaction vessel by programmed temperature increase. The programmed temperature increase is to heat to 100°C at a rate of 2°C. Solvothermal reaction for 48 h, stirring reaction for 48 h, natural cooling, and removal.

[0083] (d) Post-processing: The solid liquid was obtained by centrifugation at 9000 rpm, and then washed multiple times with acetone and deionized water. The solid wash was placed in a refrigerator and frozen for 6 hours, and then placed in a low-temperature vacuum freeze dryer for 10 hours to dry. The modified graphene powder was then removed.

[0084] The epoxy resin organic dispersion is an epoxy resin and a 1,4-dioxane solvent in a mass ratio of 1:1.5-2.

[0085] Comparative Example 1: A method for preparing a graphene-containing aqueous coating composition, comprising the following steps:

[0086] (1) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant and Dow Corning AFE-1410 defoamer were placed in a reaction vessel according to the ratio and homogenized at 1300 rpm for 7.5 min to obtain a dispersion.

[0087] (2) Add epoxy resin, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (1), homogenize at 1300 rpm for 7.5 min, add the remaining deionized water and stir evenly.

[0088] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir and mix thoroughly for 35 min, then cure at 35°C for 75 min.

[0089] The weight proportions of each component in the coating are as follows: epoxy resin 55 parts; TBEP plasticizer 2.5 parts; TEGO270 wetting agent 0.6 parts; BD-3033 leveling agent 0.25 parts; Acrysol R8 thickener 0.2 parts; ammonia water 0.3 parts; BYK163 dispersant 5 parts; Dow Corning AFE-1410 defoamer 0.35 parts; curing agent 35 parts; deionized water 10 parts.

[0090] Comparative Example 2: A method for preparing a graphene-containing aqueous coating composition, comprising the following steps:

[0091] (1) Preparation of modified graphene powder.

[0092] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder were placed in a reaction vessel according to the ratio and homogenized at 1300 rpm for 7.5 min to obtain a dispersion.

[0093] (3) Add epoxy resin, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1300 rpm for 7.5 min, add the remaining deionized water and stir evenly.

[0094] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir and mix thoroughly for 35 min, then cure at 35°C for 75 min.

[0095] The weight proportions of each component in the coating are as follows: epoxy resin 55 parts; modified graphene powder 17.5 parts; TBEP plasticizer 2.5 parts; TEGO270 wetting agent 0.6 parts; BD-3033 leveling agent 0.25 parts; Acrysol R8 thickener 0.2 parts; ammonia water 0.3 parts; BYK163 dispersant 5 parts; Dow Corning AFE-1410 defoamer 0.35 parts; curing agent 35 parts; deionized water 10 parts.

[0096] Modified graphene powder is prepared by the following steps: (a) Pretreatment: Commercially available graphene powder is placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid are added to form a mixed acid solution. The solution is heated to 95°C, cooled and refluxed with cooling water for 4.5 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid is separated and frozen in a refrigerator for 5.5 hours. Then it is dried in a low-temperature vacuum freeze dryer for 8 hours, and the fluffy modified graphene powder is taken out.

[0097] Comparative Example 3: A method for preparing a graphene-containing aqueous coating composition, comprising the following steps:

[0098] (1) Preparation of modified graphene powder.

[0099] (2) Deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder were placed in a reaction vessel according to the ratio and homogenized at 1300 rpm for 7.5 min to obtain a dispersion.

[0100] (3) Add epoxy resin emulsion, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1300 rpm for 7.5 min, add the remaining deionized water and stir evenly.

[0101] (4) Continue to add diaminodiphenyl sulfone curing agent to step (3) and stir and mix thoroughly for 35 min, then cure at 35°C for 75 min.

[0102] The weight proportions of each component in the coating are as follows: 55 parts epoxy resin emulsion; 17.5 parts modified graphene powder; 2.5 parts TBEP plasticizer; 0.6 parts TEGO270 wetting agent; 0.25 parts BD-3033 leveling agent; 0.2 parts Acrysol R8 thickener; 0.3 parts ammonia; 5 parts BYK163 dispersant; 0.35 parts Dow Corning AFE-1410 defoamer; 35 parts curing agent; and 10 parts deionized water.

[0103] Modified graphene powder is processed through the following steps: (a) Pretreatment: Commercially available graphene powder is placed in a reaction vessel, and then concentrated nitric acid and concentrated sulfuric acid are added to form a mixed acid solution. The solution is heated to 95°C, cooled and refluxed with cooling water for 4.5 hours, and then cooled to room temperature. After multiple filtrations and washings, the brown graphene solid separation is placed in a refrigerator and frozen for 5.5 hours. Then it is placed in a low-temperature vacuum freeze dryer and dried for 8 hours. The fluffy graphene powder is then removed.

[0104] (b) Preparation of grafted polymer: 79 mg of initiator AIBN and 4.5 ml of acryloyl chloride were dissolved in 11 ml of 1,4-dioxane solvent and then placed in a 65 ml reaction vessel. The reaction vessel was dried, purged with nitrogen, and stirred at 61 °C for 25 h.

[0105] (c) Modified graphene powder: Add 160 mg of graphene powder prepared in step (a) and 110 ml of 1,4-dioxane solvent to a reaction metal bottle filled with nitrogen and zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). After reacting at 65°C for 38 h, continuously purge with nitrogen. After natural cooling, add 230 ml of epoxy resin organic dispersion, stir and react for 48 h, and then remove after natural cooling.

[0106] (d) Post-processing: The solid liquid was obtained by centrifugation at 8500 rpm, and then washed multiple times with acetone and deionized water. The solid wash was placed in a refrigerator and frozen for 5.5 h, and then placed in a low-temperature vacuum freeze dryer for 8 h to dry. The modified graphene powder was then removed.

[0107] The epoxy resin organic dispersion is an epoxy resin and a 1,4-dioxane solvent in a mass ratio of 1:1.75.

[0108] The physical and chemical properties of Examples 2, 1, 2 and 3 were tested, mainly focusing on tensile strength, elastic modulus, tensile strain at break, flexural strength, flexural modulus and impact strength.

[0109]

[0110] Comparative Example 1 was a blank example, Comparative Example 2 was graphene modified only by acid, and Comparative Example 3 was similar to CN105385330B, which was epoxy resin modified graphene powder without hydrothermal assistance. The physicochemical properties of Example 2 were significantly better than those of Comparative Examples 1-3. The reasons may be as follows: (1) The epoxy groups modified on the surface of graphene can further participate in the curing reaction of the epoxy resin matrix, forming a strong interfacial effect of chemical bond connection, which enables graphene to effectively bear external load and improve physicochemical and mechanical properties; (2) Unreacted or buried acyl chloride groups are fully exposed under hydrothermal conditions and fully react with the hydroxyl groups in the epoxy resin, ultimately realizing the full functionalization of the epoxy resin into graphene; The fully functionalized graphene, due to the encapsulation of epoxy resin, will be greatly dispersed in the epoxy resin solution used in the subsequent coating preparation process. Under the curing reaction of the curing agent, a highly dispersed graphene epoxy resin coating structure is obtained, thereby significantly improving the physicochemical properties of the epoxy resin coating.

[0111] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-based coating composition containing graphene, characterized in that... The following quantities are included by weight: 40-70 parts of epoxy resin emulsion; 15-20 parts of modified graphene powder; 2-3 parts TBEP plasticizer; 0.5-0.7 parts of TEGO270 wetting agent; 0.2-0.3 parts of BD-3033 leveling agent; Acrysol R8 thickener 0.1-0.3 parts; 0.1-0.5 parts ammonia solution; BYK163 dispersant 4-6 parts; Dow Corning AFE-1410 defoamer, 0.2-0.5 parts; 30-40 parts of curing agent; 5-15 parts deionized water; The modified graphene powder was prepared through the following steps: (a) Pretreatment: Place commercially available graphene powder in a reaction vessel, then add concentrated nitric acid and concentrated sulfuric acid to form a mixed acid solution, heat to 90-98℃, cool with water and reflux for 4-5 hours, then cool to room temperature, filter and wash multiple times, place the brown graphene solid separation in a refrigerator to freeze for 5-6 hours, then put it into a low temperature vacuum freeze dryer to dry for 6-10 hours, and take out the fluffy graphene powder; (b) Preparation of grafted polymer: Dissolve 68-90 mg of initiator AIBN and 4-5 ml of acryloyl chloride in 10-12 ml of 1,4-dioxane solvent, and then place them in a 60-70 ml reaction vessel. After the reaction vessel is dried and purged with nitrogen, it is stirred at 60-62 °C for 20-30 h. (c) Modified graphene powder: Add 150-170 mg of graphene powder prepared in step (a) and 100-120 ml of 1,4-dioxane solvent to a nitrogen-filled reactor with zero moisture. After stirring evenly, seal and dropwise add all the polymer prepared in step (b). After reacting at 60-70℃ for 36-40 h, continuously introduce nitrogen gas. After natural cooling, add 220-240 ml of epoxy resin organic dispersion, seal the reactor, and use nitrogen gas to control the gas pressure of the reactor reaction gas to 6-7 MPa. Turn off the nitrogen gas supply and heat the reactor by programmed temperature increase. The programmed temperature increase is to heat to 95-100℃ at a heating rate of 1-2℃. Solvothermal reaction for 24-48 h, stirring reaction for 48 h, natural cooling, and removal. (d) Post-processing: Centrifuge at 8000-9000 rpm to obtain solid liquid, then wash with acetone and deionized water multiple times, freeze the solid wash in a refrigerator for 5-6 hours, and then dry in a low-temperature vacuum freeze dryer for 6-10 hours to remove the modified graphene powder.

2. The waterborne coating composition containing graphene as described in claim 1, characterized in that... The curing agent is a polyamine-based curing agent.

3. The graphene-containing aqueous coating composition as described in claim 2, characterized in that... The curing agent is selected from ethylenediamine or diaminodiphenyl sulfone.

4. The method for preparing a graphene-containing aqueous coating composition as described in claim 1, characterized in that... Includes the following steps: (1) Preparation of modified graphene powder; (2) According to the ratio, place part of deionized water, part of TEGO270 wetting agent, part of BYK163 dispersant, Dow Corning AFE-1410 defoamer and modified graphene powder into a reaction vessel, and homogenize at 1200-1400 rpm for 5-10 min to obtain a dispersion. (3) Add epoxy resin emulsion, TBEP plasticizer, BD-3033 leveling agent, remaining TEGO270 wetting agent, remaining BYK163 dispersant, Acrysol R8 thickener and ammonia to the dispersion obtained in step (2), homogenize at 1200-1400 rpm for 5-10 min, add the remaining deionized water and stir evenly; (4) Continue to add curing agent to step (3) and stir thoroughly for 30-40 minutes, then cure at 30-40℃ for 60-90 minutes.

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